/*
 * StringArrayTransform.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.transform;

import java.util.regex.Pattern;

/**
 * The <code>StringArrayTransform</code>  is used to transform string
 * arrays to and from string representations, which will be inserted
 * in the generated XML document as the value place holder. The
 * value must be readable and writable in the same format. Fields
 * and methods annotated with the XML attribute annotation will use
 * this to persist and retrieve the value to and from the XML source.
 * <pre>
 *
 *    &#64;Attribute
 *    private String[] array;
 *
 * </pre>
 * As well as the XML attribute values using transforms, fields and
 * methods annotated with the XML element annotation will use this.
 * Aside from the obvious difference, the element annotation has an
 * advantage over the attribute annotation in that it can maintain
 * any references using the <code>CycleStrategy</code> object.
 *
 * @author Niall Gallagher
 */
class StringArrayTransform implements Transform<String[]> {

    /**
     * Represents the pattern used to split the string values.
     */
    private final Pattern pattern;

    /**
     * This is the token used to split the string into an array.
     */
    private final String token;

    /**
     * Constructor for the <code>StringArrayTransform</code> object.
     * This will create a transform that will split an array using a
     * comma as the delimeter. In order to perform the split in a
     * reasonably performant manner the pattern used is compiled.
     */
    public StringArrayTransform() {
        this(",");
    }

    /**
     * Constructor for the <code>StringArrayTransform</code> object.
     * This will create a transform that will split an array using a
     * specified regular expression pattern. To keep the performance
     * of the transform reasonable the pattern used is compiled.
     *
     * @param token the pattern used to split the string values
     */
    public StringArrayTransform(String token) {
        this.pattern = Pattern.compile(token);
        this.token = token;
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param value this is the string representation of the value
     * @return this returns an appropriate instanced to be used
     */
    public String[] read(String value) {
        return read(value, token);
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param value this is the string representation of the value
     * @param token this is the token used to split the string
     * @return this returns an appropriate instanced to be used
     */
    private String[] read(String value, String token) {
        String[] list = pattern.split(value);

        for (int i = 0; i < list.length; i++) {
            String text = list[i];

            if (text != null) {
                list[i] = text.trim();
            }
        }
        return list;
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param list this is the value to be converted to a string
     * @return this is the string representation of the given value
     */
    public String write(String[] list) {
        return write(list, token);
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param list  this is the value to be converted to a string
     * @param token this is the token used to join the strings
     * @return this is the string representation of the given value
     */
    private String write(String[] list, String token) {
        StringBuilder text = new StringBuilder();

        for (int i = 0; i < list.length; i++) {
            String item = list[i];

            if (item != null) {
                if (text.length() > 0) {
                    text.append(token);
                    text.append(' ');
                }
                text.append(item);
            }
        }
        return text.toString();
    }
}
